ExtJS: UpdateWindow won't save true values

So I followed the Doodles tutorial to setup an Extra with a CMP, which worked great. After that, I altered the DB Schema a bit and added more fields to the CMP Grid and Update windows. So far, so good.

What I noticed now during testing is that I can't save boolean values through the UpdateWindow. Everything works fine when applying changes directly through the grid, yet in the Create or Update windows only changes to textfields seem to persist.

When I checked out the actual HTTP-Requests, I saw that the updated values are in fact being sent, in the response header all the boolean values are set to false, however. I can't find any fault with my JS, as I am new to Ext and all the processors/connectors are identical to the ones in the tutorial.

Any ideas where I could focus my search? I'll happily provide my code if deemed necessary.

Maybe this: http://forums.modx.com/thread/78805/how-to-retrieve-boolean-values-from-modx-combo-boolean#dis-post-434432

Thank Jako, you nugded me into the right direction. In my processor, when I log the $this->object->_fields array, The boolean values contain the string "Yes". I have now hotfixed this in the beforeSave() method, though I am not yet quite happy with it.
Is there a possibility to make the ExtJS combo-boolean box send the correct values (true/false or 1/0 instead of Yes/No) in the first place? It does that with updates from the grid which probably come as JSON, but not with the updates from the updateWindow which come as text.

In the status quo I'd have to add extra code for every additional boolean field to come and possibly even for every locale (haven't tested different locales so far).